Antimicrobial activity of silver nanoparticles supported by magnetite

Antibacterial and antifungal ability of silver nanoparticles (Ag NPs) supported by functionalized magnetite (Fe₃O₄) with 5-aminosalicylic acid (5-ASA) was tested against Gram-negative bacteria Escherichia coli, Gram-positive bacteria Staphylococcus aureus and yeast Candida albicans. Characterization of materials including transmission electron microscopy, X-ray diffraction analysis, and inductively coupled plasma optic emission spectroscopy technique followed each step during the course of nanocomposite preparation. The synthesized powder consists of 30–50 nm in size silver particles surrounded by clusters of smaller (∼10 nm) Fe₃O₄ particles. The content of silver in the nanocomposite powder was found to be slightly above 40 wt.–%. Concentration-dependent and time-dependent bacterial reduction measurements in dark indicated that use of Ag NPs leads to the complete reduction of E. coli and S. aureus even at the concentration level of silver as low as 40 μg/mL. However, the negligible antifungal ability of synthesized nanocomposite was found against yeast C. albicans in the entire investigated concentration range (0.1-2.0 mg/mL of the nanocomposite, i. e., 40–800 μg/mL of silver). Complete inactivation of E. coli and S. aureus was achieved in five repeated cycles indicated that synthesized nanocomposite can perform under long-run working conditions. From the technological point of view, magnetic separation is the additional advantage of synthesized nanocomposite for potential use as an antibacterial agent. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim